Contact device for key switches



Dec. 27, 1927.

R. PUDELKO CONTACT DEVICE FOR KEY SWITCHES Filed 001;. 6, 1924 lm enlorr umrso ATENT T BICOARD P'UDELKO, F ZUG, SWITZERLAND, ASSIGNOR T0 LANDIS & GYR. AwGL, 0F ZUG, SWITZERLAND, A SWISS FIRM.

CONTACT DEVICE FOR KEY SWITCHES.

Application filed October 6, 1924, Serial No. 742,041, and in Switzerland Gctober 10, 1923.

So-called ke switclies, that is to say switches in which butt contacts are pressed together by a spring and are separated from one another in order to interrupt the circuit,

have the disadvantage that the contacts often do not make sound contact over their Whole surface and only touch at one point. Apart from the poor contact, this causes rapid deterioration of the contact parts, due

to the sparking, and hence these switches can be employed for small currents only.

The object of the present invention is to eliminate the aforementioned disadvantages.

According to the invention one contact part at least is domed at the point of contact, and the other is provided with a slot at the point of contact, so that contact is obtained at more than one point.

The accompanying drawing shows one form which the invention may take, Fig. 1 being a side elevation and Fig. 2 a plan.

The moving contact 1 is mounted on a splin blade 2 and the fixed contact 3 is slotted curved portion 5 representing the surface of a cylinder. The curvature of the cyhndrical surface 5 and the slot both run in the direction of the spring blade 2, and thus contact is obtained along two lines.

With the arrangement described sound contact is obtained, inasmuch as the contact a key switch at the point of contact. The con-' 26 tact 1 is curved at the point of contact, the

1 fits snugly against the contact 4 and makes contact with it along two lines. Moreover, rapid cooling of the contacts is assured since 85 the surface of one of the contacts is considerably increased, due to the groove 4. These advantages make it possible to employ of the type described for much heavier currents than has been possible 40 hitherto.

If desired, the fixed contact 3 could be domed and the moving contact could be provided with the slot. Alternatively the surface of the one' contact might be spherical.

Also both contacts could be domed.

What I wish to secure by .U. S. Letters Patent is:

A contact device for key switches comprising a solid fixed member and a movable 60 member, said fixed member presenting a relatively large plane contact surface and a groove therein extending to said surface and substantially medially arranged, the said movable member presenting a convex surface to bear. and establish contact on said plane surface of the first named member at a plurality of points along a line extending from edge to edge of said plane surface of the first named member excepting the width of *0 said groove, said convex surface extending v in the same direction as said grooove.

In witness whereof I afi'ix my signature.

RICCARD PUDELKO. 

